MySQLi foreach bind_param() - php

Question

I'm sending an array of values from a form. I want to loop through the database table looking for these IDs. As I get this message I understand something is wrong...
Fatal error: Call to a member function bind_param() on a non-object in /home/d15155/tool/pdf.php on line 56
if (count($_POST['q']) == 0){
}
else {
foreach($_POST['q'] as $quality){
# Prepare statement
$stmt = $mysqli->prepare("SELECT the_question, the_sub_questions, the_quality, the_time FROM my_questions WHERE the_category='2' AND the_headline='5' AND quality_id = ? ORDER BY the_sort_order ASC");
$stmt->bind_param('i', $quality);
$stmt->execute();
$stmt->store_result();
$stmt->bind_result($the_question, $the_sub_questions, $the_quality, $the_time);
$stmt->fetch();
$konkretaexempel .= utf8_encode($the_question) . " <br />";
}
}
I want to add the results into a long string (then to be used in a PDF).
EDIT
Removed the foreach and the array and it still getting the same error message. I have checked and the database connection is OK.
if (count($_POST['q']) == 0){
}
else {
$stmt = $mysqli->prepare("SELECT the_question, the_sub_questions, the_quality, the_time FROM my_questions WHERE the_category='2' AND the_headline='5' AND quality_id = ? ORDER BY the_sort_order ASC");
$stmt->bind_param('i', '27');
$stmt->execute();
$stmt->bind_result($the_question, $the_sub_questions, $the_quality, $the_time);
$stmt->fetch();
$konkretaexempel .= utf8_encode($the_question) . " <br />";
}

Answer 1

Sean's tip in the comments is probably more than a side note here; it will get rid off the problem: There can be only one active query/statement per connection and after the single ->fetch() the statement is still active (a while-loop would fix that, but no need for that here). When you re-use the $stmt instance as suggested any old result set will be discarded.
Your script currently is like
<?php
$mysqli = setup();
if (count($_POST['q']) == 0){
myErrorHandling();
}
else {
foreach($_POST['q'] as $quality){
$stmt = $mysqli->prepare("SELECT x, y FROM soFoo WHERE id = ?");
if ( !$stmt ) { die('prepare failed'); }
$stmt->bind_param('i', $quality);
$stmt->execute();
$stmt->bind_result($x, $y);
$stmt->fetch();
printf("x=%d,y=%s\r\n", $x, $y);
}
}
function setup() {
// for demonstration purposes only
$_POST = [ 'q'=> [
1,3,5
]];
mysqli_report(MYSQLI_REPORT_STRICT);
$mysqli = new mysqli('localhost', 'localonly', 'localonly', 'test');
$mysqli->query('
CREATE TEMPORARY TABLE soFoo (
id int auto_increment,
x int,
y varchar(32),
primary key(id)
)
');
$stmt = $mysqli->prepare('INSERT INTO soFoo (x,y) VALUES (?,?)');
$stmt->bind_param('ss', $x, $y);
foreach( range('a','z') as $x=>$y ) {
$stmt->execute();
}
return $mysqli;
}
and the output is
x=0,y=a
prepare failed
Now when I move the calls to prepare/bind_param to before the loop
<?php
$mysqli = setup();
if (count($_POST['q']) == 0){
myErrorHandling();
}
else {
$stmt = $mysqli->prepare("SELECT x, y FROM soFoo WHERE id = ?");
if ( !$stmt ) { die('prepare failed'); }
$stmt->bind_param('i', $quality);
foreach($_POST['q'] as $quality){
$stmt->execute();
$stmt->bind_result($x, $y);
$stmt->fetch();
printf("x=%d,y=%s\r\n", $x, $y);
}
}
function setup() {
... same as before...
}
the output is
x=0,y=a
x=2,y=c
x=4,y=e
as expected.